There are various and different valve designs that have been, and currently are, used to control the flow of fluids. Air is considered a fluid for the purposes of fluid dynamics. Some of these valves are used in internal combustion engines.
A poppet valve, also called a mushroom valve, is a simple legacy design from the steam power era when the primary design criteria was to either hold or immediately evacuate mass pressure. A poppet valve consists of a hole and a tapered plug at the end of a rod or shaft called a valve stem. The valve stem is often spring loaded to keep the valve closed unless a force is applied to the end of the valve stem that is sufficient to overcome the spring force. When the plug is forced away from the hole, pressure passes rapidly from one side of the valve to the other. The poppet valve was designed and intended for use where there is no concern for consequential flow pattern, pressure, etc, and is commonly used on the intake and exhaust ports of internal combustion engines. The ideal application for a poppet valve is in systems where the most frequent conditions require the valve to stay closed.
A barrel valve has a rotating section that aligns flush with the wall of the pipe when the valve is fully open, eliminating any obstructions to flow. When rotated 90 degrees, the section is perpendicular to the pipe and completely blocks flow. Every position between fully open and fully closed presents some degree of obstruction on one side of the pipe (asymmetric) and disrupts smooth flow through the valve. A double barrel valve, where two barrel valves operating in opposite directions close toward the center of the flow chamber, somewhat alleviates this asymmetric obstruction problem, but doubles the complexity of the valve system creates a need to synchronize the two barrel valves with each other. Barrel valves are best suited for situations where the most frequent conditions require fully open unobstructed flow.
Butterfly valves function by means of a plate that rotates 90 degrees between fully closed and fully opened. When fully closed, the plate sits perpendicular to the pipe and blocks flow. When fully open, the plate sits parallel to the pipe and the fluid flows around the plate. Butterfly valves are popular because they offer a small usable range of control between open and closed where the rate of flow can be adjusted. In an automobile, this type of valve is often used on the air intake for throttling. One disadvantage of the butterfly valve is that even in the fully open position, the fluid must flow around the side profile of the plate, so there is always at least a small interruption to the flow, and a resulting pressure differential that substantially increases with heat soak. Another disadvantage of the butterfly valve is the limited range within which flow and pressure can be controlled. Flow and pressure between zero and 20 degrees open is erratic and unpredictable, and changes very little between 70 and 90 degrees open. This leaves a limited range of usable near-linear control between 20 and 70 degrees open.
The Butterfly valve is popular for its economic and simple design and is often designed to fit a given flow size without considering performance limitations. In conditions where frequent pressure drops and increases occur, the butterfly valve performs poorly outside of very narrow control ranges. The central location and counter directional movement of the disc itself creates a non-linear pressure differential between the separated chambers during the disc's overall transition. One can only precisely measure flow, pressure, velocity, etc., and time subsequent-dependent activities so long as the valve is in a fixed position or the measured range of motion is near the fully opened position. The closer that the valve's transitional movements are to the fully closed position, the more difficult it is to precisely measure resulting flows, pressures, velocities, etc. If a butterfly valve frequently and quickly moves throughout its entire range of motion, as is the case in a throttle application, calculations and subsequent timed events become impossible to measure and control with a useful degree of accuracy. This is due to a process gain that is very high at low travels and very low at higher travels. Butterfly valves do not perform very well outside a control range from about 30 percent to 50 percent open. They tend to be difficult to control at low travels, below 30 percent, because of high gain in this region and sluggish above 50 percent because of low gain. This valve may be sized to handle a specific flow within its control range, but if process conditions change, that valve may be asked to perform beyond its control range, resulting in a loss of stability and growing inefficiency. This is why the butterfly valve requires expensive, high resolution motor drive systems and electronic management controls in order to maximize operation in its efficiency range.
None of the valve designs (poppet, barrel, or butterfly) described above are intended for, or ideal for use in, conditions where frequent transitional and full range valve motion occurs with changing air velocity, pressure, and direction. There are drawbacks, even for the butterfly valve, when used in an internal combustion engine throttle body.
Current designs of baffles for inducing rotational motion in the fluid or air flow consist of static design features along the inner wall at fixed locations along the flow path. These static features are not capable of adjustment for different flow rates, or different valve positions. Therefore, an ideal rotational motion for a particular flow rate must be determined and fixed at design time. No prior art baffle designs were intended for, or are ideal for use in, conditions where frequent transitional and full range valve motion occurs, producing changing air velocity, pressure, and direction.
Therefore there is a need in the art for a valve capable of predictably controlling flow rate at all valve positions between fully closed and fully open. A system is needed for utilizing flow rate and direction control components to facilitate centralized airflow direction, expansion, and compression that are generally consistent with demands of the flow control system during all operations and positions of the valve, from fully opened to fully closed. Ideally, the valve opening should hold consistent in shape throughout the operating range while changing primarily in size and remaining centered within the pipe or housing. These features help to accomplish predictable flow characteristics throughout the operating range of the valve. These and other features and advantages of the present invention will be explained and will become obvious to one skilled in the art through the summary of the invention that follows.